Casing



FIG. 1 is a plan view of the casing;

FIG. 2 is an isometric view of the casing;

FIG. 3 is a side view of the casing; and,

FIG. 4 is an end view of the casing.

The broken line showing of the environment is for illustrative purpose only and forms no part of the claimed design. 

The ornamental design for casing, as shown and described. 